Tube bending apparatus



y 15, 1950 s. w. ALSPAUGH ETAL ,507,748

TUBE BENDING APPARATUS 4 Sheets-Sheet 1 Filed Jan. 28, 1948 y 1950 s; w. ALSPAUGH ET AL 2,507,748

TUBE BENDING APPARATUS 4 Sheets-Sheet 2 Filed Jan. 28, 1948 INVENTOR.

6 M v. L w a U m 5 BY HEN/$31: NIc/(A'L.

y 1950 s. w. ALsPAUGH ETAL 2,507,748

TUBE BENDING APPARATUS Filed Jan. 28, 1948 4 Sheets-Sheet 3 Sam/:1. M AL-SPAUGH.

H511? Q E. NICKEL.

,Mm'ua.

y 6, 1950 s. w. ALSPAUGH ETAL 2,507,748

TUBE EENDING APPARATUS Filed Jan. 28, 1948 4 Sheets-Sheet 4 III A INVENTOR. 511M047- W. 144 smuwl. BY flewgg f, Mew.

III. A 7701: NIH:

Patented May 16, 1950 TUBE BEN DING APPARATUS Samuel W. Alspaugh and Henry E. Nickel, Dayton, Ohio, assignors to General Motors Corporation, Dayton, Ohio, a corporation of Delaware Application January 28, 1948, Serial No. 4,906

3 Claims.

This invention relates to a method of and an apparatus for bending tubes.

The present invention pertains to the formation of return bend tubes or U-shaped tubes of the type employed in the construction of heat exchangers, such as cooling units and condensers, for refrigerating systems or the like and utilized to connect straight runs or lengths of a plurality of tubes together. Heretofore the operation of bending a straight piece of tubing and particularly short pieces thereof, in addition to being a slow and difficult task, also resulted in much Waste of material. We therefore propose to speed up, facilitate and eliminate the difficulties in the operation of forming or bending tubes into return bends for the purpose specified while at the same time reducing waste of material to a minimum.

An object of our invention is to provide an improved method of and apparatus for bending straight lengths of tubing into U-shaped or return bends.

Another object of our invention is to provide an apparatus of high speed and increased efficiency for bending straight lengths of tubing into return bends while at the same time improving the quality of such bends.

A further object of our invention is to provide a passageway extending from its opening on one side of a retaining member inwardly thereof and having a U-shaped curve therein with walls corresponding to the diameter of the outer walls of a tube to be forced along the passageway in such a manner that an equal radial pressure is maintained on the outer circumferential wall surfaces of the tube throughout its movement along the passageway and around the curve therein as to cause the formation of a smooth surfaced return bend in the tube.

A still further object of our invention is to provide an apparatus with separable elements each of which have a curved groove in a face thereof complementary with one another when the elements are in faceto-face registration to form a passageway adapted to receive a short tube and to provide the apparatus with a movable device having a plunger part for engaging and forcing a tube into and along the passageway and around the curve therein so as to cause bending of the tube into a form corresponding to the curvature of the passageway.

In carrying out the foregoing object it is a still further and more specific object of our invention to provide the tube-bending apparatus with means for synchronizing the registration and separation of the faces of the separable elements thereof with movements of the movable device portion of the apparatus, so that short tubes may be automatically fed into and bent by the apparatus and thereafter released therefrom.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred form of the present invention is clearly shown.

In the drawings:

Fig. 1 is a top plan view of our improved tubebending apparatus showing elements thereof in a normal or tube-receiving position;

Fig. 2 is a view similar to Fig. 1, and shows elements of the apparatus in a position after the tube has been bent therein;

Fig. 3 is a fragmentary sectional view of the apparatus taken along the lines 33 of Fig. 1;

Fig. 4 is an enlarged vertical sectional View taken on the line 4-4 of Fig. 1, showing various elements associated with the tube retaining portion of the apparatus;

Fig. 5 is an enlarged vertical sectional view taken on the line 5-5 of Fig. 1, showing a pressure connection between a movable device of the apparatus and members to be moved thereby;

Fig. 6 is an enlarged vertical fragmentary sectional view taken on the line 6-6 of Fig. 1 showing a tube adapted to be bent by the apparatus in a position to be engaged by a part of the movable device thereof;

Fig. 7 is a fragmentary view similar to Fig. 6 showing the tube being forced into the tubeforming or retaining member;

Fig. 8 is a view similar to Fig. 7 showing the completion of the tube bending operation;

Fig. 91's a view of a return bend tube formed by the present apparatus and having a further operation performed thereon; and

Fig. 10 is a view illustrating a product in which a tube bent in accordance with our invention is a part thereof.

Referring to the drawings, for illustrating the invention, we have shown an apparatus for carrying out a method of forming relatively short pieces of tubing into return bends. The apparatus is carried upon a base plate l5 supported from a suitable frame structure composed of a plurality of angle iron supports l6 (see Fig. 3). A heavy metal frame I! is interposed between the base plate l5 and the angle iron supports l6 (see Fig. 3) and has an electric motor l8 secured thereto by bolts l9 and utilized for a purpose to I 3 be hereinafter described. The base plate I is provided with a plurality of integral raised portions 2| and 22 forming shouldered reinforcin portions for backing up various elements of the apparatus mounted on the base plate. Motor I8 has a shaft 24 extending through a suitable opening in the base plate I5 and this shaft has a squared end connected, by a screw 26 (see Figs. 2 and 3), with a crank arm 21 for rotating the same. Arm 21 rotates within a circular counterbored portion 29 provided in the plate I5. A connecting rod 3| has its one end secured to the crank arm 21, by a suitable bolt or pin 32, and has a slide or movable device'33 attached to its opposite end by a wrist pin or the like 34 (see Figs. 1 and 2). Such elements and their connections are conventional and are employed to change a rotary motion of the shaft 24 into a reciprocating motion for moving the slide or device 33 toward and away from a member to be presently described. The movable device 33 has, on each of its sides, a tapered surface 36 which bears against and slides along a tapered track 3'! provided on racks 38, secured to base plate I5 by screws 39, which racks are reinforced or backed up by the integral raised portions 22 on the plate I5 (see Fig. 5). Device 33 has a pair of ear-like members 4| bolted thereto, by bolts and which members 4-I extend outwardly from opposite sides of the movable device. A rod or plunger 44 extends outwardly from the front end of the device or slide 33 and is secured to a block 46 mounted on the slide 33 by bolts 41. The attachment of rod or plunger 44 to the block 46 includes a conventional lock-nut arrangement indicated at 43 in Figs. 1 and 2 of the drawings, which provides means for adjusting the distance between the end of rod or plunger 44 and the front end of slide or device 33. The end portion of rod or plunger 44 is under-cut as at 5|, to provide a shoulder 52, and is rounded or tapered as at 53 (see Fig. 6) for a purpose to be hereinafter described. A guiding block 55, provided with holes 56 and 51 in upstanding portions 58 and 59 respectively (see Fig. 6), is secured to ie base l5 by bolts 5| (see Figs. 1 and 2). Hole 5'. slightl greater in diameter than the diameter of the outer wall of a tube to be passed therethrough and is provided with a tapered or countersunk entrance edge 52. A smaller block 64 secured upon block 55, by bolts 56, is provided with a channel 61 adapted to receive a relatively short piece of tube, as will be hereinafter more fully described.

Track forming blocks II are secured to base I 5, by bolts I2, and extend at right angles to the direction of extension of rod or plunger 44 and its movement with the movable device 33. A tube-retaining member including a pair of movable blocks I4 are slidably mounted within the tracks formed by the blocks TI and each of these blocks It carries a roller I6. Each roller I6 s mounted on a suitable pin secured to the legs of a threaded stud 'I'I. Nuts I8 are provided for adjustably locking the studs I? to their respective blocks i l (see Figs. 1, 2 and 4) The tuberetaining means or member of the present apparatus includes a two-part tool or die in the form of pair of elements 8| each carried by a movable 01001-1 74!. One of the elements 8| of the pair thereof is secured to one block I4 while the other of the pair of elements is secured to the other block I4 by screws 82 (see Fig. 4). The adjacent faces of elements BI are each provided with a groove '33 having a U-shaped curve 84 therein (see Figs. 6, 7 and 8). The grooves 83 are semicircular in cross-section and are adapted, when the adjacent faces of elements 8| are moved into abutting relation with one another, to provide a tube-retaining and forming passageway for a purpose to be more specifically described hereinafter. There is associated with each of the blocks 14 means for entering the grooves 83 and for applying pressure laterally at a plurality of points to a bent tube located in the passageway formed by the grooves. This means comprises three pins 35 (see Fi 4) formed as an integral part of studs 8! which have a threaded part threaded into an upright support 88 stationarily mounted, as by screws 89, upon the base plate IE. The supports 88 are located within a hollowed-out portion 9| of blocks I4 and the pin parts 86 of the studs 81 extend through suitable holes provided in the blocks I4 and the tool ele- B-i. The hollowed-out portion 9| of each block M permits movement of each block relative to the pin or stud support 88 enclosed in the blocks I4. Each block I4 carries a short stud 93 located in a suitable hole 94 provided therefor and which stud projects downwardly into one end of an elongated slot 96 cut in the top surface of base plate I5 (see Fig. 4). A spring 91 has its one end bearing against the end of slot 96, opposite the end thereof, into which stud 93 projects, and has its other end bearing against a flat surface on the lower end of stud 93. The springs 9'. are maintained under compression and are further compressed by movement of the locks 1-4 to bring the grooved faces of elements 8! together as will be more fully described hereinafter. Base plate I5 is provided with an opening 98 beneath the elements BI of the apparatus and a chute 98 is secured to the underside of the plate It adjacent this opening for a purpose to also be presently described.

Referring again to Figs. 1, 2, 3 and 5 of the drawings it will be noted that We provide two pair of spaced apart stops IIlI and I02 adjustably mounted upon stop carrying blocks I93 and IM respectively which blocks are bolted or otherwise suitably secured to the base plate I5. A shaft I03, located on each side of the movable device part 33 of the apparatus, is adapted to be moved or slid back and forth between the stops I 0! and I02. Each shaft I 06 is provided with fiat undercut portions I01 and I08 (see Figs. 1 and 2 respectively). Each shaft I06 passes through and is supported, in slidable relation with respect to device 33, by a bearing portion I09 formed on the ear-like members 4|. Opposed and spaced apart bosses I I I formed on the ear-like members 4 I, integral with portions I09, and between which a shaft I06 extends, each carry, within a suitable hole provided therein, a plunger II3, having a beveled fiat edge II 4 and a shank portion H6 (see Fig. 5), held under compression by a spring H1, and an adjustable threaded plug H8, 50 as to maintain the edge N4 of the plungers in engagement with a shaft I06 and particularly the undercut portions I01 and I08 thereof. The head part of plungers II3 are flat and elongated and fit within a vertical slot I I9 provided in the bosses I II to prevent rotation of the plungers out of position to register with the under-cut portions I31 and I08 of shaft I06. The forward end of each shaft I 36 carries a slide member I2I provided on one of its sides with a cam I22 and provided on its other side with the squared portion I23 (see Fig. 4) which portion I23 slides Within a suitable track I24 provided in a block I26 securely fastened to the base plate I by bolts I2'I. The rollers I6, projecting from the blocks I4, register with and roll along the side of members I 2| having the cam I22 formed thereon.

The top of the apparatus disclosed may be covered by a hood or cover I3I (see Fig. 3) which may be provided with observation windows or the like in order to view operations of the apparatus. The frame structure formed by the angle irons I6 and supporting the base plate I5 may be covered with sheet metal side and end panels so as to enclose that portion of the apparatus located below the plate I5. Hood or cover I3I has a hopper or the like I32 carried thereby in any well known or conventional manner. The outlet of the hopper I32 registers with the channel 61 in block 64 and is utilized for feeding short pieces of tube into the apparatus. In Fig. 6 of the drawings we have shown a short piece of bendable metal tubing, such as a copper or the like tube I34, fed into the apparatus by way of the hopper I32 and disposed in the channel 61, provided in the tubereceiving block 64, ready to be worked upon by the apparatus in a manner to be described in the description of operation of the apparatus. The hopper I32 may be filled manually and as long as a tube I34, or a long as the plunger rod 44, is located within the channel 61 another tube cannot enter the channel 61 to cause jamming of the apparatus. While we have shown the shaft 24 of the electric motor I8 as being directly connected to the crank mechanism in the present apparatus it is to be understood that any conventional gear or other reduction means may be interposed between the motor shaft and the crank mechanism if desired. The moving parts of the apparatus and particularly the walls of the grooves 83 in the tube-retaining member or forming elements BI, are to be adequately lubricated. In order to reduce friction to a minimum while a tube is being moved along the forming passageway an oil supplying system, having a discharge pipe located above the tube entrance opening of the tube-retaining member, may be provided for discharging oil upon the walls of the passageway or walls of the grooves 83. Such an oiling system may be conventional and for this reason it has not been illustrated in the drawings. It is also to be understood that in carrying out the method herein described other forms of apparatus may be employed so long as the tube is confined or retained in the manner prescribed during bending thereof.

In the operation of the apparatus disclosed a short tube I34 is dropped from the hopper I32 into the channel 61 of block 54, intermediate the upstanding portions 58 and 59 of block 55 while the various parts of the apparatus are in their retracted position as shown in Fig. 1 of the drawings, and with the separable elements 8| of the tube-retaining tool or member out of face-to-face engagement. As motor I8 is operated shaft 24 thereof rotates crank arm 2! to move the con- V of the tube. At thetime plunger 44 begins to move tube I34 into the guiding hole 51 of guide block 55 the shafts I06, by virtue of being gripped by the spring-pressed plungers I I3, engaging the under-cut shaft portions I08, move the slide member I2I against the forward stops I02. As shafts I66 engage the stops I02 their forward movement ceases and the plungers H3 ride out of the under-cuts I08 against the tension of the springs I I1. Thus the device 33 is then permitted to move further forwardly whereupon the plungers I I3 are forced, by springs I I1, into the undercuts Hi l on shafts I06 for a purpose to be presentli described. The slide members I 2| upon being moved forwardly cause the cams I22 thereon to force rollers I0, blocks I4 and consequently elements BI inwardly or toward one another against the pressure of the springs 97 to thereby further compress these springs. Thus the elements 8I of the tube-retaining portion of the apparatus are brought into abutment or in a faceto-face engagement with one another, as shown in Fig. 2 of the drawings, to provide a tube confining member having a passageway formed therein with an opening at one edge of the memher in registration with the guiding hole 51 in block 55. The grooves 83 in elements 8| are of such depth that the diameter of the passageway, formed by the abutting elements 8!, is substantially the same as the diameter of the outer wall of the tube I34 to thus provide a tube-confining passageway. The movement of elements 8| into face-to-face engagement obviously moves the grooves 83 therein away from the stationary pins 86 so that the passageway is readied to receive the tube L34. At the time elements BI are closed against one another tube I34 is forced by the plunger 44, through the guide hole 51 and into the confining passageway formed by the grooves 83. The end portion of the tube I34, opposite the end thereof engaged by plunger 44, moves around the U-shaped curve 84 (see Fig. 7) and further forward movement of plunger 44 moves the tube I34 to the position shown in Fig. 8 of the drawings whereby the ends of the return bend tube are in vertical alignment with one another. An inherent function of the guide hole 5? is to limit lateral movement of that portion of the flexible metallic tube I34 intermediate its ends while the same is being forced, by plunger 44, into and along the confining or bending passageway so as to avoid the formation of ripples or ridges on the outer wall surface of the tube which would interfere with its movement into and along the tube bending passageway. Guiding of tubing I34 by the wall of guide hole 57 in block 55 and by virtue of the fact that the diameter of the passageway, formed by the grooves 83, is substantially the same as the outside diameter of the tube an equal radial pressure is maintained by walls of the passageway on the outer circumferential surfaces of the tube throughout its movement along the passageway. This equal pressure applied in all radial directions to the tube during its confinement in and movement along the passageway and movement of a portion thereof around the U-shaped curve in the passageway causes the metal tube 34 to be bent into a return bend or into a shape conforming to the shape of the passageway without buckling so as to produce a return bend tube having smooth walls.

The motor I8 continues operation to retract the movable device I3, the elements secured thereto, and to cause separation of tool elements 'Bl for releasing the formed return bend tube from the apparatus. For example, when the device 33 is in its :forward position as illustrated in Fig. 2 of the drawings, with the plunger H3 engaging and fitting in the under-cut portions ill! of shafts I06, and begins its return to the retracted position as illustrated in Fig. 1 of the drawings, the plungers it cause the shaft I36 to move back against stops Hll. Upon striking the stops lfll return movement of the shaft H16 ceases and the plungers H3 ride out of the under-cut portions I01 of the shafts and along the rounded portion thereof until they are forced into the under-cut portions I08 which readies the shafts for their next forward movement. During the initial return movement of shafts IE6, the cam 22 on the slide members I21, carried by the shafts 85, moves back away from the rollers 16 and the compression springs 91 are then rendered effective automatically to move the blocks i l and consequently the elements 8i outwardly away from one another to separate the faces of elements 8| .on a line centrally of the passageway provided by the grooves 83 therein. This movement of blocks M and elements 81 relatively to the stationary supports 88 causes the pins or pegs 85 to enter the grooves 83 and apply pressure at a plurality of points to the outer wall of bent tube I34 to release the same from the forming or retaining tool should it stick in one of the grooves (see Fig. 4) The released tube I34 falls through the opening 98 in base plate and is conveyed by the chute 99 out of or away from the apparatus. The retracting movement of device 33 also moves the plunger rod M back to the position illustrated in Figs. 1 and 6 of the drawings, so as to be ready to engage and apply force to another tube fed into the apparatus from the hopper I32, as the motor H3 continues to operate.

The tube !34 formed into a return bend, after having been released from the apparatus is placed into another machine which performs a swaging operation on the ends of the return bend tube to diminish the diameter of these ends as indicated at I in Fig. 9 of the drawings. This swaging operation renders the return bend tube capable of being inserted into and secured to the end of straight lengths of tube employed in the manufacture of heat exchangers, such as condensers or evaporators of refrigerating systems or the like. As an example of the use of such return bend tube, we have illustrated in Fig. 10 of the drawings a fragment of a condenser comprising end supports I4l, straight lengths of pipe or tube i l-2 having fins I63 thereon and the return bend tubes I34 connecting adjacent ends of the pipes or tubes I42 together in fluid flow conducting relationship. The swaged ends $35 of return bend tube I34 fit into and are brazed or otherwise suitably secured to the pipes or tubes M2 to provide fluid-tight joints therebetween.

From the foregoing it will be apparent that we have provided an improved method of and apparatus for producing tubular return bends at a rapid rate to thereby reduce manufacturing cost while at the same time improving the quality of such bent tubes and minimizing waste material. The high speed possible with a method and apparatus of the type disclosed will reduce operating cost and affords high production.

While the form of embodiment of the invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, as may come within the scope of the claims which follow.

What is claimed is as follows:

1. In an apparatus of the class described comprising in combination, paired separable elements each having a face adapted to abut against one another, a groove in the face of each of said elements extending from an edge thereof and having a U-shaped curve inwardly of said edge, said elements when their faces are in abuttin relation providing a tube-retaining member and the grooves therein forming complementary wall parts of a passageway extending into said member, means for directing a tube into alignment with the opening of said passageway, a device having a part thereof adapted to engage and force a portion of said tube into and along said pasageway in said retaining member and around the curve therein to form a return bend in the tube, means for moving said device toward and away from said retaining member, means for maintaining the faces of said elements in abutting relation during movement of said device toward said tube-retaining member, means for separating the faces of said elements from one another upon movement of said device away from said retaining member, and means movable into the groove of each of said elements of the retaining member during separation of said faces thereof.

2. In an apparatus of the class described comprising in combination, paired separable elements each having a face adapted to abut against one another, a groove in the face of each of said elements extending from an edge thereof and having a U-shaped curve inwardly of said edge, said elements when their faces are in abutting relation providing a tube-retaining member and the grooves therein forming complementary wall parts of a passageway extending into said member, means for directing a tube into alignment with the opening of said passageway, a device having a part thereof adapted to engage and force a portion of said tube into and along said passageway in said retaining member and. around the curve therein to form a return bend in the tube, means for moving said device toward and away from said retaining member, means rendered effective by movement of said device toward said conduit retaining member for maintaining the faces of said elements thereof in abutting relation, and spring means for separating the faces of said elements from one another upon movement of said device away from said retaining member.

3. In an apparatus of the class described comprising in combination, paired separable elements each having a face adapted to abut against one another, a groove in the face of each of said elements extending from an edge thereof and having a U-shaped curve inwardly of said edge, said elements when their faces are in abutting relation providing a tube-retaining member and the grooves therein forming complementary wall parts of a passageway extendin into said member, means for directing a tube into alignment with the opening of said passageway, a device having a part thereof adapted to engage and force a portion of said tube into and along said passageway in said retaining member and around the curve therein to form a return bend in the tube, means for moving said device toward and away from said retaining member, means rendered effective by movement of said device toward said conduit retainin member for maintaining the faces of said elements thereof in abutting relation, spring means for separating the faces of said elements from one another upon movement UNITED STATES PATENTS of said device away, from said retaining member, Number Name Date and means movable into the groove of each of 204 527 Brady June 1878 said elements of said retaining member during 1 370074 vassen n Mar 1921 separation of the faces thereof by said. spring 5 1;370:075 vasseli 1921 meansv 2,002,470 Cornell, Jr May 21, 1935 SAMUEL ALSPAUGH- 2,335,342 Kvarnstrom Nov. 30, 1943 HENRY E. NICKEL.

REFERENCES CITED 10 The following references are of record in the file of this patent: 

